The present invention relates to holders for prosthetic heart valves, and, more particularly, to a holder for a flexible prosthetic tissue valve.
Prosthetic heart valves are used to replace damaged or diseased heart valves. In vertebrate animals, the heart is a hollow muscular organ having four pumping chambers: the left and right atria and the left and right ventricles, each provided with its own one-way outflow valve. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves. The valves of the heart separate chambers therein, and are each mounted in an annulus therebetween. The annuluses comprise dense fibrous rings attached either directly or indirectly to the atrial and ventricular muscle fibers. Prosthetic heart valves can be used to replace any of these naturally occurring valves, although repair or replacement of the aortic or mitral valves are most common because they reside in the left side of the heart where pressures are the greatest. In a valve replacement operation, the damaged leaflets are excised and the annulus sculpted to receive a replacement valve.
The four valves separate each ventricle from its associated atrium, or from the ascending aorta (left ventricle) or pulmonary artery (right ventricle). After the valve excision, the annulus generally comprises a ledge extending into and defining the orifice between the respective chambers. Prosthetic valves may attach on the upstream or downstream sides of the annulus ledge, but outside of the ventricles to avoid interfering with the large contractions therein. Thus, for example, in the left ventricle a prosthetic valve is positioned on the inflow side of the mitral valve annulus (in the left atrium), or on the outflow side of the aortic valve annulus (in the ascending aorta).
Two primary types of heart valve replacements or prostheses are known. One is a mechanical-type heart valve that uses a ball and cage arrangement or a pivoting mechanical closure to provide unidirectional blood flow. The other is a tissue-type or xe2x80x9cbioprostheticxe2x80x9d valve which is constructed with natural-tissue valve leaflets which function much like a natural human heart valve, imitating the natural action of the flexible heart valve leaflets which seal against each other to ensure the one-way blood flow.
Prosthetic tissue valves comprise a stent having a rigid, annular ring portion and a plurality of upstanding commissures to which an intact xenograft valve or separate leaflets of, for example, bovine pericardium are attached. The entire stent structure is typically cloth-covered and a sewing ring is provided around the periphery for attaching to the natural annulus. Because of the rigidity of the material used in the stent and/or wireform, conventional valves have a diameter that is minimally affected by the natural motion of the heart orifice. In the aortic position, the commissures extend in the downstream direction a spaced distance from the walls of the downstream aortic wall. Movement of the aortic wall or sinuses does not directly affect movement of the cantilevered commissures, though fluid flow and pressures generated by movement of the walls ultimately does cause the commissures to dynamically flex to some extent (i.e., they are cantilevered downstream in the aorta). Because of the inherent rigidity in conventional heart valves, the natural dilatation of the annulus is restricted, imposing an artificial narrowing of the orifice, and increasing the pressure drop therethrough.
Accordingly, there is a need for a more flexible heart valve that responds to the natural motions of the annulus and downstream vessel walls.
The present invention provides a holder for a heart valve including a flexible stent that allows relative cusp movement or pivoting. The continuous maintenance of leaflet orientation at the commissures provides durability and predictability. Though the leaflets are not wholly independent, they are allowed to move in regions of greatest anatomical motion. The heart valve may be highly flexible and include a stent/leaflet subassembly having a peripheral stent and a plurality of leaflets disposed therewithin. The stent/leaflet subassembly defines alternating cusps and the commissures. A connecting band may be attached to the stent/leaflet subassembly and follows the alternating cusps and commissures. The band may include a free edge extending from the stent for connecting the heart valve to an anatomical orifice.
In one aspect of the invention, a holder for attaching to and holding a flexible heart valve is provided. The heart valve is of the type that has multiple leaflets joined together at a periphery of the valve at valve commissures that are generally axially aligned and evenly disposed about a valve axis, the valve commissures are located between adjacent curvilinear valve cusps along the periphery of the valve. The holder comprises a plurality of cusp supports arranged around an axis to contact the heart valve generally along the valve cusps, and a plurality of commissure supports connected to and intermediate each two cusp supports and arranged to abut the valve commissures. The commissure supports are desirably radially flexible enabling the valve commissures to be flexed inward while in contact with the holder commissure supports. For example, the commissure supports may be made of Nitinol. Preferably, at least one leg extends radially inward from a cusp support to a location surrounded by the plurality of cusp supports, and more preferably multiple legs extend radially inward from each cusp support and attach together at a common location. The common location may be on the axis of the holder that coincides with the valve axis when the holder and valve are attached.
A connector may be provided extending along the holder axis to which the legs join. The connector has a coupling for receiving a handle for the holder and a length suitable for manually grasping. In one embodiment, the connector is formed separately from the legs and joined thereto. In addition, the legs may be formed separately from the cusp supports and joined thereto.
In an exemplary form, the cusp supports are multiple pieces joined together, wherein each piece may include two halves of adjacent cusp supports and a commissure support. In the multiple piece embodiment, multiple legs may extend radially inward from each cusp support and attach together at a common location, wherein each piece has two leg halves extending radially inward from each of its cusp support halves, and wherein each pair of adjacent leg halves makes up one of the holder legs.
The holder may further include a central hub with a plurality of radially outward upper legs connected to the commissure supports, and a plurality of lower legs angled downward and outward connected to the cusp supports. Each lower leg preferably has a width from the hub to a terminal end that is greatest at the terminal end to provide more surface area to contact the corresponding valve cusp.
Another aspect of the invention is a combined flexible heart valve and holder. The combination includes a prosthetic flexible heart valve having multiple leaflets joined together at a periphery of the valve at valve commissures that are generally axially aligned and evenly disposed about a valve axis. The valve commissures are configured for radial movement with respect to the valve axis and are each disposed between adjacent curvilinear valve cusps along the periphery of the valve. The valve leaflets coapt along the valve axis and curve in a direction to form an inflow side and an outflow side of the valve. The combination includes a holder attached to the outflow side of the valve having cusp supports that contact and axially support the valve cusps. The holder also has commissure supports between each two of the cusp supports that axially support the valve commissures yet permit radial their radial movement with respect to the valve axis.
The holder preferably includes structure for substantially preventing torsional deformation of the flexible heart valve during implantation. The holder further may include a valve contacting portion having a generally continuous curvilinear structure conforming to the periphery of the valve and defining the alternating cusp and commissure supports. A central hub with a plurality of legs angled downward and outward may be connected to the cusp supports. In one version, the valve contacting portion is integrally formed separate from the legs, while in another the valve contacting portion is formed of a plurality of separate pieces, each piece defining at least a part of one of the legs. Each separate piece may define a half of two adjacent cusp supports, and may be formed of a wire.
The combination further may include commissure attachment sutures connecting the commissure supports to the valve commissures. The flexible heart valve may include a sewing band that generally conforms to the valve cusps and commissures, wherein the commissure attachment sutures connect the commissure supports to the sewing band at the valve commissures. The holder further may include a valve contacting portion having a generally continuous curvilinear structure conforming to the periphery of the valve and defining the alternating cusp and commissure supports, wherein the commissure attachment sutures are severable at the commissure supports and wherein the commissure supports include leaflet guard sections that structurally protect the valve leaflets from being cut by a blade in severing the commissure attachment sutures.
The combination further may include cusp attachment sutures connecting the cusp supports to the valve cusps. The flexible heart valve may include a sewing band that generally conforms to the valve cusps and commissures, wherein the cusp attachment sutures connect the cusp supports to the sewing band at the valve cusps. Desirably the cusp attachment sutures are routed so as to cross a common cut point on the holder such that the plurality of attachments between the cusp supports and valve cusps can be severed with one cut. The holder may further include a central hub with a plurality of legs angled downward and outward connected to the cusp supports, wherein the cusp attachment sutures each loop through the valve at the valve cusps with one segment being tied to the cusp support and a second segment extending up the corresponding leg to the hub, across the common cut point. A sleeve may surround each leg within which the second segment is contained.
The holder may include two stages, a first stage having the cusp supports and a second stage having the commissure supports, the two stages being formed so as to be separable. The first stage may include a central hub and a plurality of legs angling outward and downward to form the cusp supports at their terminal ends. The second stage may include a flexible band around which the commissure supports are spaced, the band permitting the commissure supports to flex radially with respect to one another.
In another aspect of the present invention, a holder is provided for mounting the flexible heart valve. The holder includes a central hub with a plurality of radially outward upper legs, and a plurality of lower legs angled downward and outward. The upper and lower legs are adapted to connect to the alternating cusps and commissures of a flexible valve so as to maintain the position of the valve during implantation.
The present invention further provides a combination of a flexible prosthetic heart valve and a rigid holder. The flexible heart valve includes alternating cusps and commissures in a generally cylindrical configuration adapted to move radially in and out with respect to one another. The holder includes structure for maintaining a relatively fixed shape of the flexible prosthetic heart valve during implantation.
The present invention further provides a method of implantation of a heart valve, including the steps of: providing a flexible heart valve having alternating cusps and commissures in a generally cylindrical configuration and adapted to move radially in out with respect to one another; attaching a holder to the valve that restricts relative axial and torsional movement of the cusps and commissures; positioning the heart valve in proximity to an anatomical orifice; implanting the heart valve; and, disconnecting the holder from heart valve. The holder may include cusp supports that contact and axially support the valve cusps and commissure supports between each two of the cusp supports that axially support the valve commissures yet permit radial their radial movement with respect to the valve axis. In the latter case, the method may include visualizing the site of valve implantation by flexing one of the valve commissures radially inward while being supported by the corresponding commissure support of the holder.